Stiffness effects on repeatability of positioning of linear axes

Guangming Sun,Yimiao Wang,Wenjin Wang,Jinjun Liu,Ming Yu,Jian Zhao 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.9

This paper studies the effect of stiffness (including slider stiffness and bearing stiffness) on the repeatability of the positioning of linear axes. First, a mathematical model between stiffness and the repeatability of the positioning of linear axes is established. The effects of the stiffness of the slider and bearing on the repeatability of positioning are analysed. The theoretical results show that the repeatability of the positioning decreases as the slider component stiffness and bearing stiffness increases. Second, a finite element analysis is implemented to calculate the effect of slider stiffness on the repeatability of positioning, the simulation results are found to be consistent with the theoretical results. Finally, the effect of bearing stiffness on the repeatability of positioning is experimentally investigated. The experimental and theoretical analysis results have been observed to coincide. Thus, the accuracy of the theoretical analysis is verified by both simulation and experimental results. The derived results afford designers and engineers a scientific basis for the stiffness design theory.

Experimental research on the mechanisms of condensation induced water hammer in a natural circulation system

Sun, Jianchuang,Deng, Jian,Ran, Xu,Cao, Xiaxin,Fan, Guangming,Ding, Ming Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.11

Natural circulation systems (NCSs) are extensively applied in nuclear power plants because of their simplicity and inherent safety features. For some passive natural circulation systems in floating nuclear power plants (FNPPs), the ocean is commonly used as the heat sink. Condensation induced water hammer (CIWH) events may appear as the steam directly contacts the subcooled seawater, which seriously threatens the safe operation and integrity of the NCSs. Nevertheless, the research on the formation mechanisms of CIWH is insufficient, especially in NCSs. In this paper, the characteristics of flow rate and fluid temperature are emphatically analyzed. Then the formation types of CIWH are identified by visualization method. The experimental results reveal that due to the different size and formation periods of steam slugs, the flow rate presents continuous and irregular oscillation. The fluid in the horizontal hot pipe section near the water tank is always subcooled due to the reverse flow phenomenon. Moreover, the transition from stratified flow to slug flow can cause CIWH and enhance flow instability. Three types of formation mechanisms of CIWH, including the Kelvin-Helmholtz instability, the interaction of solitary wave and interface wave, and the pressure wave induced by CIWH, are obtained by identifying 67 CIWH events.

DISPERSION OF PRISTINE MULTI-WALLED CARBON NANOTUBES IN COMMON ORGANIC SOLVENTS

GUOXING SUN,ZHENGPING LIU,GUANGMING CHEN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.2

The dispersion of pristine multi-walled carbon nanotubes in various common organic solvents and water has been investigated. Sedimentation tests, optical microscopy, transmission electron microscopy and Tyndall effect tests are employed. The results clearly show that N-methyl-2-pyrrolodone, acetone, tetrahydrofuran and dichloromethane are good solvents to debundle and disperse the multi-walled carbon nanotubes. In contrast, much precipitation can be obviously observed for systems of the carbon nanotubes in water, ethanol and toluene. Additionally, Tyndall effect tests suggest that the upper dispersions of the carbon nanotubes in acetone, tetrahydrofuran and dichloromethane with a concentration of 0.1 mg/mL and the dispersion of carbon nanotubes in N-methyl-2-pyrrolodone with a concentration of 0.05 mg/mL are colloidal systems rather than solutions. Finally, based on the above results, a possible mechanism is briefly discussed.

An Adaptive JPEG Steganographic Method Based on Weight Distribution for Embedding Costs

( Yi Sun ),( Guangming Tang ),( Yuan Bian ),( Xiaoyu Xu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.5

Steganographic schemes which are based on minimizing an additive distortion function defined the overall impacts after embedding as the sum of embedding costs for individual image element. However, mutual impacts during embedding are often ignored. In this paper, an adaptive JPEG steganographic method based on weight distribution for embedding costs is proposed. The method takes mutual impacts during embedding in consideration. Firstly, an analysis is made about the factors that affect embedding fluctuations among JPEG coefficients. Then the Distortion Update Strategy (DUS) of updating the distortion costs is proposed, enabling to dynamically update the embedding costs group by group. At last,a kind of adaptive JPEG steganographic algorithm is designed combining with the update strategy and well-known additive distortion function . The experimental result illustrates that the proposed algorithm gains a superior performance in the fight against the current state-of-the-art steganalyzers with high-dimensional features.

Stress Distribution and Failure Characteristics for Workface Floor of a Tilted Coal Seam

Jian Sun,Lianguo Wang,Guangming Zhao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9

A mechanical model for the tilted workface floor along the tilted direction of coal seam was proposed. Stress expressions of an arbitrary point inside the tilted workface floor were deduced. Calculation formula for the maximum failure depth of the lateral floor strata of the tilted workface was also deduced. Based on the Mohr-Coulomb yield criterion, the tilted workfacefloor’s stress distribution, and failure depth and shape were simulated by using FLAC3D software for different coal seam’s dip angles, buried depths, and workface widths. Results show that the concentration coefficient, the peak value and the distance between the peak position of the lateral abutment pressure and the roadway on both sides of the tilted workface decreases with the increases in coal seam’s dip angle. The vertical stress isoclines present a “spoon-shaped” distribution along the tilteddirection of workface. Both sides of the workface form “bubble-shaped” distribution shear stress and its peak value increases first and then decreases with the increases in coal seam’s dip angle and reaches maximum at 30°–35°. The tilted workface floor’s plastic failure zone presents a “spoon-shaped” distribution along the tilted direction of workface, which is large on the lower side and small on the upper side. The plastic zone’s failure depth increases first and then decreases with the increases in the dip angle of coal seam and reaches maximum at 30°.

An Improved Spatially Selective Noise Filtration for Real-time Denoising of Acoustic Emission Signal

Jian Wang,Guangming Li,Peng Sun,Ruijuan Jiang,Yiyan Chen 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.7

The denoising of acoustic emission (AE) signal plays an important role in structural health monitoring. This paper proposes the improved spatially selective noise filtration (SSNF) which can eliminate the Gaussian white noise well. Firstly, through the comparison of different vanishing moments, “db5” is chose as the mother wavelet. And the Mallat algorithm is used in the composition and reconstruction of signal processing. Secondly, according to the signal noise ratio of wavelet reconstructed coefficients of AE signal, two coefficients are chosen to the next step. Lastly, the denoising algorithm uses the high degree of correlation between coefficients to realize the improved SSNF. Compared with the SSNF, the improved SSNF can avoid “glitches” and realize real-time denoising. And according to the simulation results, the improved SSNF can realize real-time denoising of AE signal.

Asynchronous H∞ Dynamic Output Feedback Control for Markovian Jump Neural Networks with Time-varying Delays

Yuqian Lin,Guangming Zhuang,Jianwei Xia,Wei Sun,Junsheng Zhao 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.3

In this paper, the problem of asynchronous robust H∞ dynamic output feedback control for Markovian jump neural networks with norm-bounded parameter uncertainties and mode-dependent time-varying delays is investigated. The improved delay-dependent stochastic stability conditions and bounded real lemma are obtained by introducing the relaxation variables, which reduces the conservatism caused by boundary technology and model transformation. An improved Lyapunov-Krasovskii functional is constructed using linear matrix inequalities. On this basis, the solution of robust H∞ dynamic output feedback problem and sufficient conditions for solving the problem of asynchronous dynamic output feedback controller are given respectively. Asynchronous dynamic output feedback controller is constructed to ensure that the closed-loop mode-dependent time-varying delays Markovian jump neural networks achieve different convergence speeds. The given H∞ performance index is satisfied for the delays not bigger than a given upper bound. Numerical examples are employed to show the effectiveness and correctness of the method presented in this paper.

miR‑1294 alleviates epithelial–mesenchymal transition by repressing FOXK1 in gastric cancer

Yaru Wang,Guangming Liu,Shijuan Sun,Junjie Qin 한국유전학회 2020 Genes & Genomics Vol.42 No.2

Background MicroRNAs (miRNAs) have been reported play critical roles in regulating tumor development and progression. Objective This study aimed to investigate the potential effect of miR-1294 in gastric cancer (GC). Methods Reverse transcription quantitative polymerase chain reaction (RT-PCR) were performed to verify the expression level of miR-1294 and Forkhead box protein K1 (FOXK1). Overall survival data of miR-1294 for GC was analysed by logrank test. Targetscan was used to screen potential target gene of miR-1294. Dual luciferase assay was assessed to investigate the relationship between miR-1294 and FOXK1. The miR-1294 overexpression and knockdown were designed to study the biological function of miR-1294. The migration and invasion of GC cell lines were investigated by wound healing and transwell assays. Western blotting were performed to verify the expression level of epithelial marker, mesenchymal markers and FOXK1. Overexpression of FOXK1 was designed to study the rescue effects of FOXK1 in SGC7901 cell. Results miR-1294 was found downregulated in GC patients and cell lines. A higher miR-1294 expression showed a significant longer overall survival than those with a lower miR-1294 expression. miR-1294 directly targets FOXK1 and regulates the expression of FOXK1. In addition, miR-1294 regulates epithelial-mesenchymal transition (EMT) by inhibiting FOXK1 in GC cells and it can be rescued by overexpression of FOXK1. Conclusion miR-1294 alleviates EMT process in GC by targeting FOXK1.

Comparisons and Correlations of Phenolic Profiles and Anti-oxidant Activities of Seventeen Varieties of Pineapple

Liqing Du,Guangming Sun,Xiumei Zhang,Yuge Liu,Witoon Prinyawiwatkul,Zhimin Xu,Yixiao Shen 한국식품과학회 2016 Food Science and Biotechnology Vol.25 No.2

Major phenolic, β-carotene, and ascorbic acid (AA) contents in 17 pineapple varieties were quantified and compared. Anti-oxidant activities were evaluated using 2,2-Diphenyl-l-picrylhydrazyl (DPPH), 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing anti-oxidant power (FRAP), and metal chelating capacity (MCC) assays. MD-2 exhibited the highest AA and total phenolic (TP) contents and DPPH and ABTS assay results, but was lower in β-carotene contents. Ripley had the highest total flavonoid (TF) content with a low AA content. Comte de Pairs exhibited the highest MCC and the lowest FRAP values. TP contents and both DPPH and ABTS activities, FRAP values and both AA contents and DPPH activities, and TF contents and ABTS activities were positively correlated. MD-2 exhibited the greatest diversity of phenolics and highest anti-oxidant activities in all assays. Information included herein can be useful for development of pineapple-based food products containing high levels of health promoting anti-oxidants.

Mode-dependent H∞ Filtering for Time-varying Delays Neutral Jump Systems Based on FWM Technique

Guowei Zhao,Guangming Zhuang,Jianwei Xia,Wei Sun,Junsheng Zhao,Minsong Zhang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.6

This paper is concerned with the problem of mode dependent H∞ filter for uncertainty Markovian jump system with neutral delay and retarded time-varying delay. By using free weight matrix (FWM) technique, the stability conditions of delay dependent are obtained under the framework of Lyapunov stability theory. Based on those result, the delay dependent conditions for full order and mode dependent Markovian jump linear filters are gained, which are expressed by Linear matrix inequalities (LMIs). Finally, a numerical example and a PEEC practical example are employed to prove the validity of the results.